During 1986-87 the National Survey of Oral Health in School Children was conducted by Westat Inc. in cooperation with NIDR to monitor the prevalence of oral diseases in school children, grades K-12, throughout the contiguous United States and Hawaii. The 1986-87 survey was a replication and extension of the NIDR National Dental Caries Prevalence Survey conducted in 1979-80, also by Westat, which established baseline estimates on the prevalence of dental caries, gingivitis and dental restorative treatment needs. Both surveys utilized multi-stage probability samples of over 39,000 school children enrolled in grades K- 12 to represent over 43 million children enrolled in public or private schools in the seven geographic regions of the U.S. In the 1986-87 survey, additional assessments were made for dental fluorosis, soft tissue lesions, and the use of smokeless tobacco. Residential histories, health and demographic data were collected for each child participating in the clinical examination. The objective of this ongoing collaborative effort is to develop generalized variance models for selected non-binary statistics common to both surveys, to calculate correlations between the two surveys and to measure design effects in order to establish optimal cluster sizes for future national surveys.